1. Field of the Invention
The present invention relates to a calibrating apparatus and method, and more particularly to a calibration target in a scanner.
2. Description of the Prior Art
FIG. 1 shows the external features of a scanner wherein machine base 30 includes main component parts such as, light source, sensors, analog-to-digital converter, amplifier and I/O interface. The material of transparent glass 40 on housing 20 can be replaced by other transparent materials, such as acrylic resin. Picture for scanning is downward on transparent glass 40, and lid 10 covers picture to scan where scanning direction is from A to A'.
FIG. 2 shows the inside structure of housing 20 in FIG. 1. Picture for scanning is upward under transparent glass 40. Because a dark-white calibration is necessary before scanning, a calibration target 60 is in the housing 20 of a scanner where the calibration target 60 in the front of transparent glass 40 is perpendicular to scanning direction.
The scanning direction is from A to A', and scanning order is calibration target to picture in sequence.
The structure of calibration target is a white calibrating area and a dark calibrating area, as shown in FIG. 3. The white calibrating area gives sensors white calibration and steady output, and also defines the brightness of photography. The border between white calibrating area and dark calibrating area is set up the reference of scanning origin, because distance between the border and scanning document can be determined. The dark calibrating area does not provide dark calibration. The scanning direction in calibration target is from white calibrating area 62 to dark calibrating area 64.
The fabrication of calibration target is that prints a long black bar in white board and paste on the transparent glass after appropriately cutting. However, system will have higher tolerance after cutting and sticking. Moreover, the cutting process will make more scrap materials higher cost in materials.